JP2008106626A - Cradle receiver for variable displacement axial piston pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide all of load resistance, abrasion resistance, and low frictional properties, in a cradle receiver for a variable displacement axial piston pump. <P>SOLUTION: The cradle receivers 1 for a variable displacement axial piston pump is brought into slide-contact with a cradle 3 for adjusting a stroke of a piston 2 so as to hold the cradle 3 to be capable of oscillating. On a surface side of a base member 1a of each cradle receiver 1, that is, a slide-contact face with respect to the cradle 3 is provided with a lubricating film containing fluororesin, heat resistant binder resin, and metal oxide powders, and the cradle receivers 1 are held by cradle guides 4. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a cradle receiver that slides in contact with a cradle that changes the stroke of a piston of a variable displacement axial piston pump and holds the cradle so as to be swingable, and a variable displacement axial piston pump using the cradle.

  For example, a structure of a so-called cradle type pump (hereinafter simply referred to as a pump) is well known as a variable displacement piston pump used as a hydraulic pressure generation source of a hydraulic circuit.

  In the cradle type pump, a cylinder block that accommodates a piston is integrally rotated together with a rotating shaft, and the cradle is slidably contacted with the cradle guide and supported so as to be inclined with respect to the rotating shaft. It contacts the inclined surface of the cradle via the connected shoe.

  Therefore, the piston reciprocates with a stroke defined according to the inclination angle of the cradle with the rotation of the rotating shaft, and has a pump action. The discharge capacity of the pump due to the stroke difference can be constantly changed by controlling the inclination angle of the cradle with respect to the rotation axis by hydraulic pressure or the like.

  However, for example, when a cradle made of an aluminum material (including an aluminum alloy) is held in sliding contact with a cradle guide made of the same aluminum material, the tilt angle of the cradle with respect to the rotation axis is constantly controlled by hydraulic pressure or the like. Both cause sliding wear and cause problems such as seizure. For this reason, a means has been adopted in which a synthetic resin thrust bushing is interposed between the cradle and the cradle guide.

  For example, as a thrust bush used as a cradle holder, a metal thrust bush having a resin film on a sliding surface and a thrust bush made of a slidable resin such as nylon, polyacetal, and PTFE are known (see Patent Document 1). ).

  Fluoride resin such as ethylene-tetrafluoroethylene copolymer (ETFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polytetrafluoroethylene (PTFE) or the like is attached to at least one of the cradle made of aluminum material or the cradle guide. A variable displacement piston pump provided with a coating is also known (see Patent Document 2).

  Further, as a thrust bush used as a cradle receiver, a thrust bush in which a copper-based sintered film is formed on the surface of an iron base, and a thrust bush in which a resin film is further applied to the surface of the sintered film are known (see Patent Document 3). ).

  On the other hand, in washer, vane, slide guide, guide pin, curtain wall, seismic isolation device that slides infrequently, fluorine resin such as polytetrafluoroethylene, polyamideimide resin, etc. as wear-resistant and non-adhesive coating agent A coating material containing a heat-resistant binder resin and iron oxide powder is known (Patent Document 4).

Utility Model Registration No. 2559510 JP-A-08-334081 Utility Model Registration No. 2584135 JP-A-10-120980 (paragraph [0029])

  However, normally, when the cradle contacts the cradle guide with a high surface pressure of about 10 MPa and always slides, the cradle receiver (thrust bush) described in Patent Document 1 satisfies the load resistance due to the resin film. There is a problem that you can not.

  The problem regarding the load resistance in this application is that a fluororesin coating such as polytetrafluoroethylene described in Patent Document 2 is formed on the surface of a cradle guide made of aluminum, or an iron substrate described in Patent Document 3 It can be improved by forming a fluororesin coating on the surface of the material via a copper-based sintered film, but in that case, the wear resistance and the low friction properties are not sufficient.

  Accordingly, an object of the present invention is to solve the above-described problems, that is, to satisfy all of load resistance, wear resistance and low friction characteristics in a cradle receiver of a variable displacement axial piston pump.

  In order to solve the above-described problems, in the present invention, a cradle receiver made of a metal base material that is slidably contacted with a cradle for adjusting a piston stroke in a variable displacement axial piston pump and is held so that the cradle can swing. The cradle receiver of the variable capacity type axial piston pump is characterized in that the sliding surface of the cradle receiver with respect to the cradle is provided with a lubricating film containing a fluororesin, a heat-resistant binder resin and a metal oxide powder. It is.

  The cradle receiver of the variable capacity type axial piston pump of the present invention configured as described above includes a fluororesin excellent in friction characteristics, and also has high wear resistance by including a heat resistant binder resin and a metal oxide powder. Has an excellent lubricating film. As a result, sufficient seizure resistance and wear resistance on the sliding surface can be secured, and even in a high-pressure sliding state of 10 MPa, it can satisfy all of load resistance, wear resistance and low friction characteristics and can be used for a long time. .

  Such a lubricating film sufficiently satisfies the above characteristics when the lubricating film contains 100 to 150 parts by weight of heat-resistant binder resin and 5 to 20 parts by weight of metal oxide powder with respect to 100 parts by weight of fluororesin. To become.

  Furthermore, if the metal oxide powder is an iron oxide powder, the wear resistance is more fully effective, and such a material can improve the practicality in terms of availability and price.

  Moreover, the adhesion of the cradle and the lubricating coating is improved by providing the lubricating coating on the slidable contact surface of the cradle receiver made of the metal base material with the base layer made of the metal porous layer. Lubricant film containing metal oxide powder is thought to be compatible with and adheres to the fine irregular surface of the metal porous layer, thereby making it possible to withstand load and wear in the aforementioned high-pressure sliding state. In addition, the low friction characteristics can be satisfied sufficiently for a long time.

  In addition, the variable displacement type axial piston pump can control the tilt angle of the cradle precisely by providing the cradle receiver with such characteristics, thereby enabling the precise hydraulic control operation and the reliability to function precisely. It becomes a high pump.

  The cradle receiver of the variable displacement piston pump of the present invention is provided with a lubricating film containing a fluororesin, a heat-resistant binder resin and a metal oxide powder on the sliding contact surface with respect to the cradle. A heat-resistant binder resin that contains materials ensures high wear resistance and load resistance, and can be used for a long period of time by satisfying all load resistance, wear resistance, and low friction characteristics even in a high-pressure sliding state of 10 MPa. There is an advantage to become.

  In addition, when a lubrication film is provided via an underlayer composed of a metal porous layer, the adhesion between the cradle and the lubrication film is improved, and the load resistance and long life are improved. There is also.

  In addition, the variable displacement axial piston pump having such a cradle receiver becomes a highly functional pump with precise cradle tilt control.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
As shown in FIGS. 1 to 3, the cradle receiver 1 of the variable displacement axial piston pump is in sliding contact with a cradle 3 that adjusts the stroke of the piston 2 and holds the cradle 3 so that it can swing. The cradle receiver 1 is provided with a heat-resistant binder resin film 1b containing an oil-absorbing filler on the surface side of the base 1a of the cradle receiver 1, that is, the sliding contact surface with respect to the cradle 3. One set is held by the cradle guide 4.

  In the variable capacity type axial piston pump used in the embodiment, a rotary shaft 7 is rotatably supported between end walls of a pair of housings 5 and 6 joined, and a cylinder block 8 is relative to the rotary shaft 7. It is supported so that it cannot rotate. A plurality of pistons 2 are accommodated in a cylinder block 8 that rotates integrally with the rotary shaft 7 so as to be slidable in the axial direction of the rotary shaft 7. 7 are alternately connected to the arcuate suction port 9a and the discharge port 9b formed in the valve plate 9 in conjunction with the rotation of the valve 7. As a result, the hydraulic oil is sucked into the piston accommodating chambers 8a from the suction ports 9a, and the hydraulic oil in the piston accommodating chambers 8a in the cylinder block 8 rotated together with the rotary shaft 7 is discharged to the discharge port 9b.

  The pressing spring 10 biases the cylinder block 8 toward the cradle 3 side. As a result, the shoe 12 made of an aluminum material held by the retainer 11 around the rotating shaft 7 is brought into close contact with the flat portion of the cradle 7, and the piston 2 fitted to the shoe 12 moves to the cradle 3 as the rotating shaft 7 rotates. It is reciprocated with a stroke according to the inclination angle.

  The tilt angle of the cradle 3 is always controlled to an appropriate angle by the pressing force of the pressing spring 13 in the housing 5 and the hydraulic pressure from the cylinder 15 adjusted by the hydraulic control device 14.

  As shown in FIGS. 1 and 2, two cradle guides 4 are fixed and provided in a set 5 in an aluminum alloy housing 5, and a rotating shaft 7 is provided between the two cradle guides 4. Is disposed through the shaft hole.

  The pair of cradle guides 4 are respectively formed with support surfaces 4a and 4b for the cradle receivers in the shape of an arc, and a pair of cradle receivers 1 and 1 are provided on the support surfaces 4a and 4b for the cradle receivers. It is fixed by fitting the pair of concave portions 4 ′ and convex portions 1 ′ so as not to be displaced.

  The cradle 3 is formed of, for example, a silicon-containing aluminum alloy, and a pair of arcuate sliding contact portions 3a and 3b corresponding to the support surfaces 4a and 4b of the respective cradle receivers project from the back surface thereof. Both sliding contact portions 3a and 3b are assembled so as to be in contact with the support surfaces 4a and 4b via the pair of cradle receivers 1 and 1. The curved surfaces of the cradle receivers 1 and 1 are formed in the same shape corresponding to the arcuate surface shape of the support surfaces 4a and 4b.

  The metal base material forming the cradle receivers 1 and 1 is formed of a steel plate such as S45C or SPCC. On the sliding surface on which the cradle of the metal base 1a (see FIG. 3) of the cradle receivers 1 and 1 is slid, a lubricating film 1b containing a fluororesin, a heat-resistant binder resin and a metal oxide powder is formed. Has been.

The material containing the fluororesin, the heat-resistant binder resin and the metal oxide powder that form the lubricating film used in the present invention will be described below.
The fluororesin that forms the lubricious film has a low friction characteristic and serves to impart seizure resistance to the film. The fluororesin is not particularly limited as long as it has heat resistance capable of withstanding temperature rise at the sliding portion with the cradle. Specifically, PTFE (melting point θ _M : 327 ° C., continuous use temperature θ _A : 260 ° C. ), Tetrafluoroethylene-hexafluoropropylene copolymer (θ _M : 270 ° C., θ _A : 200 ° C.), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (θ _M : 310 ° C., θ _A : 260 ° C.) , Tetrafluoroethylene-ethylene copolymer (θ _M : 270 ° C., θ _A : 150 ° C.), polychlorotrifluoroethylene (θ _M : 210 ° C., θ _A : 120 ° C.), ethylene-chlorotrifluoroethylene copolymer And coalesced (θ _M : 240 ° C, θ _A : 150 ° C). These may be used singly or in combination of two or more types of copolymers or tricopolymers.

Among these, PTFE is composed of repeating units of —CF ₂ CF ₂ —, has a high melt viscosity of about 10 ¹⁰ to 10 ¹¹ Pa · s even at 340 to 380 ° C., and hardly flows even when the melting point is exceeded. Among these, heat resistance is most excellent, and excellent sliding property is exhibited even at room temperature. Furthermore, among PTFE, it is preferable to use a lubricant grade powder PTFE, and examples of commercially available lubricant grade powder PTFE include Polyflon M15, Lubron L-2 (trade name, manufactured by Daikin Industries), Teflon TLP-10 ( DuPont brand name), Fullon G163 (Asahi Glass brand name) and the like. Note that the lubricant-grade powder PTFE means regenerated PTFE obtained by pulverizing PTFE that has been fired once, PTFE powder obtained by subjecting PTFE to a low molecular weight by gamma irradiation treatment, and examples of commercially available products that have been subjected to gamma radiation treatment include There is KT400H (Kitamura Co., Ltd. trade name).

  The form of PTFE may be a powder for molding or a fine powder for so-called solid lubricant, and its average particle size is in the range of 0.1 to 20 μm, preferably 0.2 to 10 μm. It is good. When the average particle size is within this range, it is difficult to agglomerate in the coating agent, and it is uniformly distributed in the film.

  The heat-resistant binder resin used in the present invention firmly adheres to the porous sprayed layer without thermally degrading the coating and serves to bind the powdered fluororesin or metal oxide powder. Examples of the heat-resistant binder resin include a polyimide resin, an epoxy resin, a phenol resin, a silicone resin, and the like. Among them, the polyimide resin is most excellent in heat resistance and adhesion.

  Specific examples of the polyimide resin include polyimide resin (PI), polyamideimide resin (PAI), polyesterimide resin, and polyesteramideimide resin, among which PI and PAI are preferable, and imide bond Alternatively, an aromatic polyimide resin or an aromatic polyamideimide resin in which an amide bond is bonded via an aromatic group is particularly preferable.

  PAI is a resin having an imide bond and an amide bond. Further, the imide bond of the aromatic polyamideimide resin may be a precursor such as polyamic acid, a closed imide ring, or a mixture of these. Such an aromatic polyamideimide resin is produced from an aromatic primary diamine (for example, diphenylmethanediamine) and an aromatic tribasic acid anhydride (for example, a mono- or diacyl halide derivative of trimet acid anhydride). And those produced from an aromatic diisocyanate compound (for example, diphenylmethane diisocyanate) and an aromatic tribasic acid anhydride. Furthermore, it is produced from an aromatic, aliphatic or alicyclic diisocyanate compound and an aromatic tetrabasic acid dianhydride and an aromatic tribasic acid anhydride as PAI having a higher ratio of imide bonds than amide bonds. Any PAI can be used.

  The metal oxide powder used for this invention plays the role which improves the abrasion resistance of a membrane | film | coat, and powders, such as an iron oxide, a titanium oxide, magnesium oxide, an aluminum oxide, can be used.

  As a method for forming the above-mentioned lubricating film on the surface of the metal substrate, the coating agent having the above-described configuration is applied to the surface of the porous sprayed layer by dipping, spray coating, brush coating, powder coating, or the like. The method of apply | coating and baking this is employable. When the coating agent is applied by the spray coating method, the coating agent becomes fine particles and adheres to the surface of the metal substrate, so that the thickness of the coating can be accurately controlled.

  The above coating agent can be obtained by dispersing or dissolving a fluororesin, a heat-resistant binder resin, and a metal oxide powder in a solvent except when a powder coating method is employed. Solvents include ketones such as acetone and methyl ethyl ketone, esters such as methyl acetate and ethyl acetate, aromatic hydrocarbons such as toluene and xylene, and organic halogenated compounds such as methyl chloroform, trichloroethylene and trichlorotrifluoroethane. Aprotic polar solvents such as NMP, DMAC, methylisopyrrolidone (MIP), and dimethylformamide (DMF) can be used. The powder coating method is solventless coating.

  The film thickness of the lubricating film applied to the metal substrate by these methods is 5 to 40 μm, preferably 10 to 30 μm, after the firing. If the film thickness is less than 5 μm, local wear may occur when uneven sliding contact with the cradle occurs, and if the film thickness exceeds 40 μm, the film tends to peel off.

  The firing temperature of the lubricating film varies depending on the kind of the heat-resistant binder resin constituting the coating agent, but when the heat-resistant binder resin is PI, 200 to 350 ° C. is appropriate. If the firing temperature is less than 200 ° C., the imide reaction of the polyamic acid that is the precursor is not sufficient, and there is a risk that sufficient adhesion with the metal substrate may not be ensured. If it exceeds 350 ° C., the fluororesin exceeds the melting point. Because it begins to decompose.

  When the heat-resistant binder resin is PAI, the firing temperature of the film is suitably 180 to 280 ° C. If the firing temperature is less than 180 ° C., the PAI curing reaction does not proceed so much, so that sufficient adhesion to the metal substrate cannot be secured, and if it exceeds 280 ° C., the fluororesin starts to decompose above the melting point. It is. Moreover, since the adhesiveness of the PAI to the metal base material reaches an equilibrium state at around 280 ° C., it is preferable to fire at 280 ° C. or lower in consideration of the temperature rising energy.

  By making the lubricating film into 100 parts by weight of the fluororesin, the heat-resistant binder resin is 100 to 150 parts by weight, and the metal oxide powder is 5 to 20 parts by weight. The adhesion and wear resistance can be better exhibited. If the heat-resistant binder resin is less than 100 parts by weight with respect to 100 parts by weight of the fluororesin, the adhesiveness is lowered, and if it exceeds 150 parts by weight, the sliding characteristics are lowered. Further, if the amount of the metal oxide powder is less than 5 parts by weight with respect to 100 parts by weight of the fluororesin, the wear resistance is insufficient, and if it exceeds 20 parts by weight, the adhesion is lowered.

  By using the metal oxide powder as the iron oxide powder, the wear resistance can be further improved, which is advantageous in terms of availability and cost.

  As the iron oxide powder, iron oxide (II), ferric trioxide, triiron tetroxide and the like can be used, and the powder shape of these iron oxides is any shape such as a spherical shape, a scale shape, and a needle shape. It may be. The average particle diameter of the iron oxide powder may be any particle diameter, for example, about 0.1 to 10 μm, but is preferably 0.1 to 1 μm, more preferably 0.2 to 0.5 μm.

  When the average particle size is less than 0.1 μm, the particles are easily aggregated and the dispersibility is deteriorated. When the average particle size is more than 1 μm, the wear resistance of the film becomes slightly nonuniform. The average particle diameter of the iron oxide powder can be measured by the BET method, but is not particularly limited to this measurement method.

  Moreover, in order to improve the adhesiveness of a base material and a lubricous membrane | film | coat, it is preferable to form a metal porous layer on the surface of a base material. Examples of the metal porous layer include a metal sintered layer and a metal sprayed layer, and the metal sprayed layer is preferable because the adhesion between the base material and the lubricating film is superior to the metal sintered layer.

  As the metal of the metal porous layer, Cu, Al, Fe, Ni, Mo, or the like can be selected. The metal porous layer may have any thickness, but is preferably 10 to 500 μm, specifically 20 to 200 μm, and more preferably 50 to 100 μm, for example. When the thickness is less than 10 μm, local ground exposure occurs in the layer, and a uniform metal porous layer cannot be obtained. On the other hand, when the thickness exceeds 500 μm, the variation in film thickness increases.

[Examples 1-6, Comparative Examples 1-3]
Test pieces serving as cradle receivers of Examples and Comparative Examples were produced by the following method. That is, after degreasing a steel (SPCC) sliding member (25 mm × 50 mm), a lubricating film was formed on the surface using a coating agent having the composition (parts by weight) shown in Table 1.

  The coating agent for film formation used in Examples and Comparative Examples was prepared as follows.

  The coating agent used in the examples was prepared by dissolving the PAI resin in N-methyl-2-pyrrolidone (NMP) at the blending ratio shown in Table 1, and blending this resin solution with a fluororesin and a metal oxide. A coating composition is prepared by diluting with a mixed solvent of N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), xylene and ethyl acetate so that the solid concentration is about 23 to 35% by weight. Obtained.

  The coating agent used in the comparative example is a coating agent prepared in the same manner as in the example except that the compounding ratio shown in Table 1 is used without compounding the metal oxide.

  Using these coating agents, a cradle receiving test plate having a lubricating film was prepared. First, a coating agent was sprayed onto the surface of a plate (25 mm × 50 mm) of an SPCC base material by a spray coating method so that the thickness of the lubricated film after firing was about 40 μm. After drying, it was baked at a maximum temperature of 240 ° C. and naturally cooled to obtain a test piece having a lubricating film.

  A frictional wear (reciprocating motion) test was performed in a sliding state with respect to these sliding member aluminum alloy counterparts. The test conditions are shown below, and the results are also shown in Table 1.

[Test conditions]
Testing machine: NTN reciprocating testing machine Surface pressure: 12MPa
Maximum excitation speed: 2.95 m / min
Amplitude: + -50mm
Temperature: Room temperature Lubrication condition: Oil lubrication Test time: 2000 reciprocations (initially, 500 times, 1000 times, coefficient of friction is measured)

  As is apparent from the results in Table 1, Comparative Examples 1 to 3 tend to have a high friction coefficient when reciprocating 1000 times, and it was recognized that they cannot withstand long-term use.

  On the other hand, in Examples 1 to 4, in the reciprocation test, the coefficient of friction was low until the end of the test, and no change was observed in the state of the film. As a result, it was confirmed that the cradle receiver of the example can withstand long-term use of the variable displacement piston pump by the basic test, and can satisfy all of load resistance, wear resistance and low friction characteristics. .

Vertical section of variable displacement axial piston pump Exploded perspective view showing cradle, cradle holder and cradle guide Sectional view showing the cradle holder held by the cradle guide

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cradle receptacle 1a Base material 1b Heat resistant binder resin film 2 Piston 3 Cradle 3a, 3b Sliding contact part 4 Cradle guide 4a, 4b Support surface 5, 6 Housing 7 Rotating shaft 8 Cylinder block 8a Piston accommodating chamber 9 Valve plate 9a Suction port 9b Discharge port 10 Pressing spring 11 Retainer 12 Shoe 14 Hydraulic control device 15 Cylinder

Claims (5)

In a cradle receiver made of a metal base material that is slidably contacted with a cradle that adjusts a piston stroke in a variable displacement type axial piston pump and is held so that the cradle can swing,
A cradle receiver for a variable capacity axial piston pump, characterized in that a lubricating film containing a fluororesin, a heat-resistant binder resin and a metal oxide powder is provided on a sliding surface of the cradle receiver with respect to the cradle.   The variable capacity type according to claim 1, wherein the lubricating film is a lubricating film containing 100 to 150 parts by weight of heat-resistant binder resin and 5 to 20 parts by weight of metal oxide powder with respect to 100 parts by weight of the fluororesin. Axial piston pump cradle.   The cradle receiver of a variable capacity type axial piston pump according to claim 1 or 2, wherein the metal oxide powder is iron oxide powder.   The variable capacity type axial according to any one of claims 1 to 3, wherein a lubricating film is provided on a slidable contact surface of the cradle receiver made of a metal base material with respect to the cradle via a base layer made of a metal porous layer. Piston pump cradle receiver.   A variable displacement axial piston pump comprising the cradle receiver according to claim 1.

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